Add new path module

Implements [RFC 474](https://github.com/rust-lang/rfcs/pull/474); see
that RFC for details/motivation for this change.

This initial commit does not include additional normalization or
platform-specific path extensions. These will be done in follow up
commits or PRs.

src/libstd/ffi/mod.rs

@@ -24,6 +24,7 @@
 mod c_str;
 mod os_str;
 
+// FIXME (#21670): these should be defined in the os_str module
 /// Freely convertible to an `&OsStr` slice.
 pub trait AsOsStr {
     /// Convert to an `&OsStr` slice.

src/libstd/ffi/os_str.rs

@@ -41,7 +41,7 @@
 use ops;
 use cmp;
 use hash::{Hash, Hasher, Writer};
-use path::{Path, GenericPath};
+use old_path::{Path, GenericPath};
 
 use sys::os_str::{Buf, Slice};
 use sys_common::{AsInner, IntoInner, FromInner};

src/libstd/sys/unix/os_str.rs

@@ -20,7 +20,7 @@
 use string::{String, CowString};
 use mem;
 
-#[derive(Clone)]
+#[derive(Clone, Hash)]
 pub struct Buf {
     pub inner: Vec<u8>
 }

src/libstd/sys/windows/os_str.rs

@@ -18,7 +18,7 @@
 use option::Option;
 use mem;
 
-#[derive(Clone)]
+#[derive(Clone, Hash)]
 pub struct Buf {
     pub inner: Wtf8Buf
 }

src/test/run-pass/issue-15149.rs

@@ -11,7 +11,7 @@
 use std::slice::SliceExt;
 use std::old_io::{Command, fs, USER_RWX};
 use std::os;
-use std::path::BytesContainer;
+use std::old_path::BytesContainer;
 use std::rand::random;
 
 fn main() {

src/test/run-pass/issue-3424.rs

@@ -1,4 +1,3 @@
-
 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
@@ -15,8 +14,8 @@
 #![feature(box_syntax)]
 #![feature(unboxed_closures)]
 
-use std::path::{Path};
-use std::path;
+use std::old_path::{Path};
+use std::old_path;
 use std::result;
 use std::thunk::Thunk;
 
@@ -28,7 +27,7 @@ fn tester()
         result::Result::Ok("more blah".to_string())
     };
 
-    let path = path::Path::new("blah");
+    let path = old_path::Path::new("blah");
     assert!(loader(&path).is_ok());
 }
 

src/test/run-pass/process-spawn-with-unicode-params.rs

@@ -20,7 +20,7 @@
 use std::old_io::fs;
 use std::old_io::Command;
 use std::os;
-use std::path::Path;
+use std::old_path::Path;
 
 fn main() {
     let my_args = os::args();